As EV adoption accelerates, performance requirements for power semiconductors are rising quickly in both on-board chargers (OBCs) and ground-installed DC fast charging infrastructure. As the market shifts from conventional silicon (Si) devices to silicon carbide (SiC) and gallium nitride (GaN), procurement and design teams need to understand topology changes, quantitative performance advantages, and functional safety requirements in one view.
EV battery voltage is moving from 400V to 800V, starting with high-performance vehicles. Higher voltage improves charging efficiency and reduces cable weight, but it also raises requirements for blocking voltage, switching loss, and thermal management in power devices.
OBC (on-board charger)
Converts AC input to DC for the battery. Covers 3.3 to 22kW. Available in unidirectional and bidirectional types. Size and weight constraints are strict because it is mounted in the vehicle.
DC fast charging (EVSE)
Ground-installed equipment. Ranges from 25kW to more than 350kW. Compliance with IEC 61851 is a baseline requirement for the European market.
V2X-ready bidirectional OBC
Enables reverse power flow for V2G, V2H, V2V, and related use cases. Wide-bandgap SiC/GaN devices are needed for bidirectional operation.
Effect of SiC adoption (vs Si)
Up to 30% lower losses, up to 50% higher power density, and up to 15% lower system cost, according to Wolfspeed data.
OBC topology shift: from unidirectional charging to bidirectional V2X
OBC charging output ranges from below 2kW for electric scooters to 22kW for premium EVs. SiC shows a clear advantage in the 6.6kW to 22kW range in particular (Wolfspeed). The basic architecture consists of two blocks: an input-side AC/DC converter (PFC stage) and an isolated DC/DC converter.
Totem-pole PFC adoption is expanding in the PFC stage. Totem-pole PFC removes the bridge rectifier, reduces the number of semiconductor devices in the conduction path from three to two, lowers losses, and enables bidirectional operation. That bidirectional capability is the physical basis for V2X use cases including V2H, V2G, and V2V. Infineon positions SiC/GaN-based wide-bandgap chips as essential for future V2L, V2H, and V2G use cases.
In the mass-market EV segment, where price competition is intensifying, Infineon observes a trend from modules toward discrete components. Scalable chipsets that can combine Si, SiC, and GaN let suppliers address multiple EV platforms with different cost sensitivities.
Quantitative effects of SiC adoption
OBCs using Wolfspeed SiC MOSFETs can reduce losses by up to 30% compared with conventional silicon. That loss reduction can simplify the cooling system and cut system cost by up to 15%, supporting the total cost of ownership (TCO) case for SiC even though the device unit price is higher than Si. Power density can improve by up to 50%, giving designers more freedom in EVs where vehicle space is tightly constrained.
As a concrete design example, Wolfspeed's 22kW three-phase bidirectional AFE converter using 1200V C3M™ SiC MOSFETs achieves 98.5% peak efficiency, 4.6 kW/L power density, and a 45kHz switching frequency in both PFC mode and inverter mode.
DC fast charging: design requirements for the 25kW to 100kW class
Ground-installed DC fast chargers require higher output than OBCs. onsemi's reference design (SEC-25KW-SIC-PIM-GEVK) uses a 1200V EliteSiC SiC power integrated module, covers a 200V to 1000V output range, and supports charging for both 400V and 800V EV battery systems. Three-phase PFC and a DAB topology also enable bidirectional power conversion, while conversion efficiency exceeds 96% across the full output range. The input specification supports both 400Vac for Europe and 480Vac for the United States.
For EV charging infrastructure in Europe, compliance with IEC 61851, the EV charging equipment standard, and EMC standard EN55011 Class A is a baseline requirement. onsemi's reference design incorporates these requirements from the design stage and can shorten the certification process. onsemi offers product families covering passenger EVs, commercial vehicles, and agricultural fleets from AC Level 1/2 to high-power Level 3 DC fast charging.
Functional safety: ASIL-D and ISO 26262
Automotive electronics must comply with functional safety standards under ISO 26262, and required safety levels are defined from ASIL-A to ASIL-D. Infineon's OBC chipset supports ASIL-D, the highest safety level, helping Tier 1 suppliers reduce the cost and time needed for individual certification.
Implications for procurement and design teams
800V support is becoming a de facto prerequisite for supplier qualification on emerging EV platforms. onsemi's OBC solutions cover 3.3kW to 22kW and up to 800V, offering choices from EliteSiC MOSFETs to hybrid IGBTs according to cost sensitivity. Hybrid SiC and Si configurations are a realistic migration path for vehicle models that need to balance mass-production cost and performance.
As Infineon notes, cost pressure can make discrete component selection more common than module adoption in some phases. Procurement strategy needs to choose between module adoption and discrete optimization based on application, production scale, and available design margin. In competitive evaluation of DC fast charger designs, conversion efficiency, power density, and IEC 61851 compliance serve as the first screening criteria.